Personal care compositions such as hair sprays, styling shampoos, cosmetics, skin care products, and the like, often contain film-forming polymers for various reasons. These film-forming polymers are especially useful in hair care compositions to provide hair styling performance to the composition. Film-forming polymers for use in such compositions include organic or silicone-containing, linear or graft, copolymers which contain various monomers in an alternating, random, block or homopolymer configuration.
Graft copolymers are well known for use as film-forming polymers in hair care and other personal care compositions. These graft copolymers typically comprise a polymeric backbone and one or more macromonomers grafted to the backbone, wherein the physical and chemical attributes such as glass transition temperature values (Tg), water solubility, and so forth are selected for the polymeric backbone and macromonomer grafts so as to provide the desired film-forming properties and other chemical or physical properties of the copolymers in a personal care composition. The graft copolymers are especially versatile in that the polymeric backbone and the attached macromonomer grafts can have select or different chemical or physical properties which collectively provide the optimal formulation or performance profile for the intended personal care composition in which it will be used.
Synthesis of graft copolymers, however, is typically more difficult than synthesis of many copolymers, especially linear polymers. Unlike linear polymer synthesis, the synthesis of graft copolymers typically involves a separate polymerization step involving the making of a macromonomer containing a reactive end group, copolymerization of the macromonomer with a copolymerizable, ethylenically unsaturated monomer, and then termination of this last copolymerization step to obtain the desired graft polymers.
It has now been found that hydrophobic and hydrophilic graft polymers can now be made by simpler, more effective synthesis methods, and that these new synthesis methods result in the formation graft polymers which when applied to the hair or other surface form a polymeric film or weld having improved adhesive and cohesive strength. These polymers are very useful when used as film-forming polymers in personal care compositions, especially when used as film-forming or styling polymers in hair styling compositions. The graft polymers in these hair styling compositions provide improved styling and/or conditioning performance, and are especially effective in providing improved durability of hair style and improved hair feel.
It is therefore an object of the present invention to provide an improved method for making graft polymers, and further to provide such a method for making graft polymers for use in personal care compositions, and yet further to provide such a method which involves fewer synthesis steps than other conventional methods of making graft polymers.